The invention relates to breakaway link assemblies for supporting shock-sensitive equipment in aligned dispositions.
Electronic equipment of the type used for missile guidance conventionally is carried by a support housing or shell which, in turn, is mounted in an airframe structural shell. To assure operational reliability and precision, the housing of the electronic components must be very precisely aligned with the airframe. Further, the alignment must be maintained during flight in which, of course, the missile is subjected to substantial vibratory disturbances as well as the forces of in-flight maneuvers. For present purposes, these in-flight acceleration forces are considered as being `normal operational conditions` which, by way of illustration, usually are substantially less than 10g.
Aside from these normal operating conditions, the protection and alignment-maintenance also must consider non-operational g-load factors. For example, the missiles require handling, transportation and storage all of which may impose load factors of a relatively low level such as 10-15g. However, in these handling phases, absolute rigidity does not have to be constantly maintained and some slight movements can be tolerated providing the support is such that realignment occurs automatically when the disturbance is removed. In other words, these relatively-low level, non-operational accelerations usually are not damaging to the shock sensitive equipment and they can be applied directly provided realignment is achieved prior to flight.
At force levels higher than those anticipated during flight or normal handling and transportation, the support problem becomes primarily one of protection rather than alignment. For example, `Missile Guidance Set` of the so-called Cruise missile probably can withstand `g` forces up to about 50g before actual damage occurs. However, when stored in a submarine, extreme load forces from `near misses` or the like must be anticipated. Such forces may be in the order of 200g which obviously would cause serious damage.
Consequently, the type of link mechanisms presently being considered are characterized by their ability, first, to provide the requisite rigid support under normal operating conditions and, next, to provide a breakaway capability when exposed to higher non-operational forces. It is recognized that there are a number of comparable devices capable of withstanding normal forces and also capable of breaking or yielding at a predetermined force level. Such mechanisms, however, although perhaps quite beneficial in their particular applications, do not appear to fulfill the present requirements. For example, rigidity or stiffness under operational conditions apparently has not been a controlling consideration. Also, these mechanisms apparently have not considered the need for a controlled yielding of the rigidity followed by an automatic realignment. Finally, from a functional viewpoint, although breakaway may be achieved, the arrangements do not easily and automatically accomplish a subsequent realignment which is essential for operational reliability.
The objects of the present invention should, for the most part, be apparent in the foregoing description. However, a further important object is one of providing a rigid, breakaway supporting and aligning link mechanism which is extermely small relative to its load capability. For example, in the Cruise missile, the isolation system `sway` space provided for the breakaway link is less than 2". With such a space limitation, springs or the like, such as frequently are used for the breakaway loading, must have very high spring rates for very short strokes. As far as is known, breakaway links of the type presently contemplated have not been adapted for such confined use.